Not all thunderstorms are severe, but all thunderstorms and thundershowers have thunder; which is caused by lightning- the underrated killer! CannonSevereWx is making the extra effort to warn you of the first lightning strike when certain charging mechanisms are seen on Doppler radar and CELLO software. This effort is not guaranteed, but is an educated guess on volunteer basis. This article describes the terminology, graphics, and reasons behind lightning prediction products seen at CannonSevereWx.
1o-Mile Lightning Perimeter
Abbreviated 10MLP, this is a yellow line circling a 10 mile perimeter around Cannon Co. Because lightning can strike 10 miles away from a storm, any lightning within this perimeter can pose danger to citizens within 10 miles of that storm. When lightning occurs inside of this perimeter, a lightning risk box or polygon will be drawn to include the approximate area in Cannon Co that the storm tracker believes could be at risk of a lightning strike.
lightning Risk Box
Lightning risk boxes or rings are issued when the storm tracker sees signs that lightning conditions are developing within 10 miles of any point in Cannon Co. In the example above, no lightning was occurring at the time, but a threat was seen developing aloft above the shower in SW Cannon Co. There were also showers approaching N Cannon Co from Murfreesboro. Since there were developing threats to N and S Cannon Co, a lightning risk box was drawn to include the entire county. How much lead-time warning did this give people inside of the risk box? Keep reading....
Increasing Risk alert
Radar updates revealed further development which showed an increasing risk of lightning. Up to this point, there were no strikes and no thunder to warn people to get out of swimming pools, and halt all outdoor activities to seek shelter. Lightning risk graphics are ALWAYS DRAWN IN YELLOW. Citizens were being warned to move indoors with escalated language and a yellow graphic highlighting the most dangerous area.
First Strike Occurred
Citizens were given a 16 minute lead-time notice before the first lightning strike. That is life-saving time and information if people receive the information and understand the First Strike prediction purpose. The two showers merged into a nasty non-severe storm with deadly frequently occurring cloud-to-ground lightning.
10-mile Radius Rings
10-mile radius rings are used when a source of electrification is known to show residents the approximate area of danger on a map. People are still warned to remain indoors when they hear thunder. In this example, there were more sources of electrification presenting danger to neighboring counties, so the risk was mentioned for those residents; although not in my coverage area.
As with Storm Prediction Center watch boxes (the wording that severe weather can happen in and near the outlined area), lightning may strike inside and near the lightning risk box or ring. First Strike alert products are not issued by the National Weather Service, but are provided exclusively by CannonSevereWx on a volunteer basis, and are not guaranteed to warn you before the first strike everytime.